atom x is sodium and then the atom y is chlorine
The generic equation for a reaction between an acid and water is

When an acid "reacts" with water, water acts as the base that accepts the proton (H+) from the acid. The remaining ion that is formed after the acid has donated its proton is called the conjugate base (

), and the conjugate acid-base pair is

-

.
Hydrogen sulfate (

) is an ion from sulfuric acid. It is still an acid in itself and can "react" with water ((

) to form the sulfate (

) and hydronium (

)ions.

Based on the previous discussion,

is identified to be the conjugate of the acid

.
Thus, the conjugate acid-base pair is
.
Answer:
- <u><em>Substance A.</em></u>
Explanation:
pH is a measure of the concentration of H₃O⁺ ions in a solution.
It is defined as:
![pH=\log \dfrac{1}{[H_3O^+]}=-\log [H_3O^+]](https://tex.z-dn.net/?f=pH%3D%5Clog%20%5Cdfrac%7B1%7D%7B%5BH_3O%5E%2B%5D%7D%3D-%5Clog%20%5BH_3O%5E%2B%5D)
For the given substances
Sustance [H₃O⁺] pH = - log [H₃O⁺]
M
A 4×10⁻⁶ -log (4×10⁻⁶) = 5.4 ← answer
B 6×10⁻⁷ -log (6×10⁻⁷) = 6.2
C error - - - - - -
D 1.3×10⁻¹ -log (1.3×10⁻¹) = 0.89
Thus, the unknown substace most likely is A.
Answer:
Th is the symbol for element Thorium.
Mg is magnesium while Mg 2+ is magnesium Ion. Judging from periodic trends, atomic radius is one half the distance between the atoms of two covalently bonded atoms. It decreases as elevtrons are added to valence shells. That means, across the period it increases and down the group it decreases. Making Mg2+ smaller.
Electronegativity is the energy needed to take an electron in the gaseous state. Florine is more electron negative that lithium. It increases across the period and decreases down the group. Except in the Noble group.
Explanation: